Why Are Thousands of Seabirds Struggling Along California’s Coast?

A common murre weighs about two pounds and needs a great deal of food for its size. It catches small schooling fish by diving, usually between 60 and 160 feet, using its wings to swim. In a normal year that works. In a marine heatwave the fish move down into cooler water or north out of the area, and every dive costs more than it returns.

The deficit compounds. A thin bird has less fat to keep warm, less energy for its immune system and, in late summer, gaps in its plumage as it moults. Rescuers in 2026 saw exactly that: emaciation, fungal lung infections, blood parasites and worn, broken feathers. This sequence is consistent with what investigators found, but it is an explanation, not proof that every bird died the same way. CDFW’s own lead investigator has said the heatwave is probably not the only factor.

Oil shows up on the feathers. Domoic acid shows up in tissue samples and in neurological symptoms. Starvation shows up as emaciation: wasted breast muscle and no fat. DDT left almost no bodies at all, just empty nests and crushed eggs. Telling these apart is the first job in any die-off, and it is why the same beach scene in 1990, 2015 and 2026 led to three different explanations.

The two sets of numbers measure different things. International Bird Rescue’s figures are live birds admitted to its two centres; Pacific Wildlife Care’s are admissions to one clinic on the central coast; CDFW’s 295 reports are dead birds reported by the public from January to April. None is a death toll. Researchers stress that birds dying miles offshore rarely drift to a beach, so every count here is a floor.

Oil is the cause most people picture, and the one where blame is easiest to assign. Yet the deadliest oil source on this coast was not a dramatic collision but a slow leak. The freighter S.S. Jacob Luckenbach sank off San Francisco in 1953 and for decades released fuel after winter storms. Because nobody reported a spill, the oiled birds that washed up were “mystery” cases until samples were matched to the wreck in January 2002. A 2006 report for California’s spill office put the toll from 1990 to 2003 at 51,539 seabirds, about 62% of them common murres.

The big visible spills also changed the law. After the American Trader in February 1990 and the Exxon Valdez the year before, Congress passed the Oil Pollution Act, which required double hulls on tankers, and California created its Office of Oil Spill Prevention and Response. Spills did not stop: Cosco Busan in 2007, Refugio in 2015 and Huntington Beach in 2021 all killed birds. But they became smaller and better documented.

The brown pelican is the coast’s clearest success and its clearest warning. DDT almost erased it from Southern California without leaving many bodies: eggs broke, chicks were never hatched. Once the chemical was banned in 1972, shells thickened, colonies refilled and the bird left the endangered list in 2009. Since 2022, though, pelicans have stranded in large numbers almost every year, from hunger, algal toxins and fishing-gear injuries. Recovery from one threat does not protect a species from the next.

Seabirds feed across several levels of the food web, so their condition reflects things that are hard to observe offshore. A die-off is not proof that a whole population is collapsing, but a run of them, as in 2014–16 and again since 2022, shows an ocean under repeated stress.